1. Field of the Invention
The present invention relates to packers, packing elements, and other downhole tools that employ an expandable element to isolate various sections of a well bore drilled in the earth from other sections of the well bore. In particular, a packer may include naturally occurring organic matter that may expand when exposed to the heat or liquids present in a wellbore. Methods of using and manufacturing such tools are also disclosed.
2. State of the Art
During the process of drilling a well, the well bore typically encounters a variety of rock formations, or stratigraphic layers. These stratigraphic layers typically include different constituent components such as minerals and fluids, including gases and liquids, of varying types. The different gases and liquids, however, typically segregate by density, with the least dense fluids (including gases) located higher within a particular rock formation. Typically, it is desirable to keep the different fluids present in a given stratigraphic layer physically separate while pumping from the well. Additionally, it is typically desirable to keep fluids and gases present in a first stratigraphic layer physically separate from the gases and fluids that are present in a second stratigraphic layer.
For example, FIG. 4 illustrates a two dimensional view of a first formation 405 that includes water, a second formation 410 that is an impermeable formation, such as shale, and a third formation 415 that includes hydrocarbons that are encountered by a well bore 425. The first formation 405 is at a relatively lower hydrostatic pressure as compared to the hydrostatic pressure present in the third, deeper formation 415, the second, impermeable formation 410 preventing the less dense (as compared to water) hydrocarbons present in the third formation 415 from migrating upwards into the first formation 405. If the formations 405 and 415 are not physically isolated from each other in some manner, whether by the formation 410 initially or a packer 10, and a path, such as a well bore 425, exists along which formation fluids 420 can flow, the fluids 420 at the higher hydrostatic pressure in the third formation 415 would flow from the third formation 415 into the lower pressure first formation 405, thereby contaminating the water present in the first formation 405. To prevent this, production tubing 430 is connected to a packer 10 that is positioned at a depth above or within the third formation 415. An impermeable element 22 provides a hydraulic seal against the formation 415, preventing formation fluids 420 present in the formation 415 from flowing around the packer and into the first formation 405 at the lower hydrostatic pressure. Instead, the formation fluids 420 flow through a conduit 21 (seen in FIGS. 2-3) of the packer 10 and into the production tubing 430 and onto the surface for processing.
Packers are used in a variety of applications, including wellbore stimulation and testing, protecting casing from the corrosive fluids that the well produces, holding treatment and kill fluids, and other applications known in the art. Packers typically include several components, including a sealing device, a setting or holding device, and, a conduit to permit the passage of fluids between the isolated zones in a controlled manner. The sealing element is expanded to isolate the annulus of an upper section of a well bore from a lower section. Packers are used in a variety of settings in which it is desirable to isolate different sections of the well bore from each other. These sections include, but not limited to, different sections of casing and production tubing set within the well bore, between casing and an unlined borehole, and separate sections of an unlined borehole, among others.
Packers are typically positioned in a wellbore by using a wireline, drill pipe, tubulars, or coiled tubing that is connected to the packer to deliver the packer to a desired depth in the well bore. Once the packer reaches a desired depth, one of a variety of mechanisms known in the art is employed to set the packer, which involves expanding a sealing element until it contacts the side of the well bore or casing, thereby isolating the section of well bore or casing above the sealing element from the section below the sealing element. A typical sealing element of a packer includes an elastomeric element located between upper and lower retaining rings, with the sealing element compressed to radially expand outwardly until it contacts the casing or borehole wall. Another common design for a sealing element is to pump a fluid, such as a gas or a liquid, into a bladder located within an elastomeric element, the fluid causing the elastomeric element to expand. Yet another known method employs elastomers that swell in the presence of hydrocarbons to create a seal.
Several shortcomings exist, however, in existing packers. Most of the methods of setting and expanding packers require the intervention of an operator at the surface, which increases the complexity of the setting operation. Further, packers that rely on mechanical or hydraulic interventions increase the risk of mechanical or hydraulic failure of the packer, both at the surface and downhole, as well as increasing the time and the cost of using the packer. In addition, the elastomers used in many packers are susceptible to corrosion and deterioration when exposed to the heat and fluids present in a wellbore, which may lead to a loss of an effective hydraulic seal, which could require a costly intervention or work-over to remedy.
Therefore, it is desirable to have a packer that operates with a minimal amount of intervention once it is positioned in the well.